Finally I lost sight of them altogether.

The coffer still continued to glow; but the lamps began to grow dim.

At first I thought that their light was being overpowered by the thick black smoke; but presently I saw that they were, one by one, burning out.

They must have burned quickly to produce such fierce and vivid flames.
I waited and waited, expecting every instant to hear the command to turn up the light; but none came.

I waited still, and looked with harrowing intensity at the rolling billows of smoke still pouring out of the glowing casket, whilst the lamps sank down and went out one by one.
Finally there was but one lamp alight, and that was dimly blue and flickering.